#include<netinet/in.h>   // sockaddr_in  
    #include<sys/types.h>    // socket  
    #include<sys/socket.h>   // socket  
    #include<stdio.h>        // printf  
    #include<stdlib.h>       // exit  
    #include<string.h>       // bzero  
      
    #define SERVER_PORT 8000  
    #define BUFFER_SIZE 1024  
    #define FILE_NAME_MAX_SIZE 512  
      
    int main()  
    {  
        // 声明并初始化一个客户端的socket地址结构  
        struct sockaddr_in client_addr;  
        bzero(&client_addr, sizeof(client_addr));  
        client_addr.sin_family = AF_INET;  
        client_addr.sin_addr.s_addr = htons(INADDR_ANY);  
        client_addr.sin_port = htons(0);  
      
        // 创建socket，若成功，返回socket描述符  
        int client_socket_fd = socket(AF_INET, SOCK_STREAM, 0);  
        if(client_socket_fd < 0)  
        {  
            perror("Create Socket Failed:");  
            exit(1);  
        }  
      
        // 绑定客户端的socket和客户端的socket地址结构 非必需  
        if(-1 == (bind(client_socket_fd, (struct sockaddr*)&client_addr, sizeof(client_addr))))  
        {  
            perror("Client Bind Failed:");  
            exit(1);  
        }  
      
        // 声明一个服务器端的socket地址结构，并用服务器那边的IP地址及端口对其进行初始化，用于后面的连接  
        struct sockaddr_in server_addr;  
        bzero(&server_addr, sizeof(server_addr));  
        server_addr.sin_family = AF_INET;  
        if(inet_pton(AF_INET, "127.0.0.1", &server_addr.sin_addr) == 0)  
        {  
            perror("Server IP Address Error:");  
            exit(1);  
        }  
        server_addr.sin_port = htons(SERVER_PORT);  
        socklen_t server_addr_length = sizeof(server_addr);  
      
        // 向服务器发起连接，连接成功后client_socket_fd代表了客户端和服务器的一个socket连接  
        if(connect(client_socket_fd, (struct sockaddr*)&server_addr, server_addr_length) < 0)  
        {  
            perror("Can Not Connect To Server IP:");  
            exit(0);  
        }  
      
        // 输入文件名 并放到缓冲区buffer中等待发送  
        char file_name[FILE_NAME_MAX_SIZE+1];  
        bzero(file_name, FILE_NAME_MAX_SIZE+1);  
        printf("Please Input File Name :\t");  
        scanf("%s", file_name);  
      
        char buffer[BUFFER_SIZE];  
        bzero(buffer, BUFFER_SIZE);  
        strncpy(buffer, file_name, strlen(file_name)>BUFFER_SIZE?BUFFER_SIZE:strlen(file_name));  
          
        // 向服务器发送buffer中的数据  
        if(send(client_socket_fd, buffer, BUFFER_SIZE, 0) < 0)  
        {  
            perror("Send File Name Failed:");  
            exit(1);  
        }  
      
     
        FILE *fp = fopen(file_name, "w");  
        if(NULL == fp)  
        {  
            printf("File:\t%s Can Not Open To Write\n", file_name);  
            exit(1);  
        }  
      
        // 从服务器接收数据到buffer中  
        // 每接收一段数据，便将其写入文件中，循环直到文件接收完并写完为止  
        bzero(buffer, BUFFER_SIZE);  
        int length = 0;  
        while((length = recv(client_socket_fd, buffer, BUFFER_SIZE, 0)) > 0)  
        {  
            if(fwrite(buffer, sizeof(char), length, fp) < length)  
            {  
                printf("File:\t%s Write Failed\n", file_name);  
                break;  
            }  
            bzero(buffer, BUFFER_SIZE);  
        }  
      
        // 接收成功后，关闭文件，关闭socket  
        printf("Send File:\t%s  Successful!\n", file_name);  
        close(fp);  
        close(client_socket_fd);  
        return 0;  
    }  
